Tonight’s episode of NCIS brings Ziva face-to-face with her longtime mentor Monique Lisson (Karina Lombard), as she and Tony head to Colombia on a mission to search for a missing Marine, but will the reunion be all it’s cracked up to be?

“This relationship goes back a while and we see a hint of what I may have been like for these two women when they were operating together, but their relationship is different….she realizes there’s something off about her,” star Cote de Pablo tells EW.

Lisson, she explains, is a woman who’s sacrificed everything in her personal life for her career – she has no husband, children or social life to speak of. And as Ziva’s surrogate big sister, Lisson is on a bit of a mission separate from their case-of-the-week. “One of the things we discover as the episode goes through is that there are things that agent Monique is trying to tell Ziva about her choices in her life. A ‘learn from me’ sort of thing – as an older sister who has gone through it and as a woman who has lost a lot along the way,” she says.

And Ziva might very well get the message, teases de Pablo. “In this particular episode, I can’t say that much happens, but at the end, there’s a moment where you may take a closer look at the way DiNozzo (Michael Weatherly) may feel for Ziva,” she says.

The episode, airing tonight at 8, is among the last of the current season of NCIS. With only four new episodes remaining before the show’s big finale on May 15, which will see the team facing off against a terrorist threat, de Pablo says viewers should prepare for anything. “I know there’s a huge thing coming up that I can’t reveal, but I also can’t reveal because these writers will tell us and then change things on us!” she says. “It keeps us on our toes. I always like to pry information our of them because I like to get excited about the work. So I like to find out as much as I can. But stuff’s going to happen and some of it may be shocking.”